1. Field of the Invention
The invention relates generally to the field of high availability electronic systems, and, more specifically, to the identification of chassis within such systems.
2. Background of the Invention
High availability systems are presently used in applications where systems are required to operate with little or no interruption of service. The telecommunications and data markets, for example, have many applications for high availability systems including central office switches, private branch exchanges (PBX), internet routers, and digital subscriber loops (DSL). Standards have been developed to facilitate communication between high availability system components built by different manufacturers.
One example of a prior art high availability system is CompactPCI. Standards for CompactPCI products are agreed to by PCI Industrial Computers Manufacturers Group (PICMG). A CompactPCI product has, among other things, a metal cover that encloses a chassis, a backplane, and slots for printed circuit boards that perform specific applications. A general description of CompactPCI can be found in PICMG 2.0 R2.1, CompactPCI Specification Short Form, published Sep. 2, 1997. A more complete description of CompactPCI can be found in PICMG 2.0 R3.0, CompactPCI Specification, published Oct. 1, 1999. Any system component that can be replaced in the field by a technician is known by one of ordinary skill in the art as a Field Replaceable Unit (FRU). In a high availability system there are, typically, mechanisms for compensating for a failure, such as, for example, redundancy. When an FRU (component or a circuit board) fails within a high availability system that has been placed in the field, it is important to notify a service provider of the failure so that the system can be repaired.
In telecommunications applications, for example, a company may have thousands of unattended systems deployed in racks all over the world. Furthermore, there may be many different chassis stacked in these racks. Before a service provider can send a technician to repair a failure, more must be communicated than simply the fact that a failure has occurred somewhere in the field. The identity of the failed chassis must be determined. A prior art means for identifying a failed chassis is disclosed in the Intelligent Platform Management Interface (IPMI) Specification version 1.5, published Feb. 21, 2001. Permission to license the IPMI specification document can be obtained from Intel Corp., Hewlett-Packard Company, NEC Corp., and Dell Computer Corp.
A product complying with IPMI may have an identification module having an Electrically Erasable Programmable Read Only Memory (EEPROM) that contains at least some identifying information that is unique to the chassis. The data stored in the EEPROM is called the chassis information. An EEPROM used to store the chassis information is called the FRU memory device (the FRU term denotes that the memory device is replaceable in the field). The chassis information is written to the EEPROM at the factory may include, among other things, the chassis serial number, date of manufacture, model number, vendor information, and product number. Blank fields may also be available for the end user to write other identification information that may be useful, such as a string or text describing the geographical location of the chassis. If a failure occurs, information about the failure is typically transmitted to a monitoring center along with the information stored in the FRU memory device.
Referring to FIG. 1, a chassis identification system 100 is shown according to the prior art. A management entity 110 oversees a group of sensors in system 100. A chassis information device 122 is coupled to a bus 136 along with other miscellaneous sensors. Prior art FRU memory devices, however, have several disadvantages. First, there is no way for the information in the identification module to be copied to other non-volatile memory for preservation in case the identification module fails. Second, there are no redundant FRU memory devices in case the primary module fails. Third, the bus coupled to the identification module may cause the module to become inoperable should the bus fail for reasons that have nothing to do with the module itself. For these and other reasons, the prior art risks losing crucial chassis identity information so that a system administrator may not be able to determine which system is having a problem from potentially thousands of deployed unmanned systems.